Boxboard carton closure

ABSTRACT

A boxboard carton has a closure which is sealed by activation of adhesive applied to facing surfaces of closure flaps near a corner of the carton, the facing surfaces being on the same side of the boxboard sheet from which the carton is made, the carton being openable without rupturing the adhesive seal.

United States Patent Perry [54] BOXBOARD CARTON CLOSURE [72] Inventor: George S. Perry, Nashua, N.H.

[73] Assignee: Universal Packaging Corporation, Concord, NH.

[22] Filed: Oct. 15, 1970 211 Appl. No.: 81,001

52 use: ..229/5lTS,229/38 51 1nt.Cl. ..B65d5/54,B65dl7/00 5s FieldofSearch ..229/51TS,51TC,51D,43,

[ 56] References Cited UNITED STATES PATENTS 2,670,128 2/1954 Stowitts ..229/38 2,864,547 12/1958 Guyer ..229/51TS [451 Feb.l,l972

2,868,432 1/1959 Guyerm. ..229/51 TS 3,132,793 5/1964 Osteex ..229/51 TS 3,507,442 4/1970 Van Dan et al. .....229/51 TS 3,520,465 7/1970 Spiering et a1 ..229/51 TS X Primary Examiner-Davis T. Moorhead Attorney-Rowland V. Patrick ABSTRACT A boxboard carton has a closure which is sealed by activation of adhesive applied to facing surfaces of closure flaps near a corner of the carton, the facing surfaces being on the same side of the boxboard sheet from which the carton is made, the canon being openable without rupturing the adhesive seal.

7 Claims, 10 Drawing Figures PATENTED FEB 1 I972 SHEET 2 BF 2 BOXBOARD CARTON CLOSURE This invention relates to boxboard cartons and more particularly to improved end closures for cartons such as are used as frozen food containers.

Filled boxboard cartons are most readily and reliably closed if their contacting closure flaps have face-to-face coatings of a thermoplastic adhesive providing a coat-to-coat contact when the flaps are pressed together and the adhesive is heated to make the seal. This means however that any carton blank made from one piece of sheet material has to have the sheet material coated with adhesive on both sides because the outer surface of the boxboard material forming one folded-in flap lies against the inner surface of the boxboard material forming the other overlapping flap. Coating both sides of the boxboard sheet material with thermoplastic adhesive is expensive particularly since usually it is only the outer surface of the boxboard which is sized for print reception purposes. Adhesives applied to the unsized or less sized inner surface often have to have a heavy application of adhesive in order to provide a useful adhesive layer if the adhesive readily sinks into the boxboard.

The present invention is concerned with securing a sealed boxboard carton having an adhesive coat-to-coat adhesive seal despite the fact that the adhesive is present on only one side of the boxboard blank.

The invention is further concerned with having the seal near a comer of the carton so that there will be better wall support during the sealing operation.

The invention is further concerned with the provision of an opening strip, familiarly referred to as a zipper, which can be torn from the package without having to break any adhesive seal.

The closure end of such a setup carton is shown in FIG. 1.

The closure is constituted of two sealing flaps l2 and 14 which can be folded counterdirectionally into overlapping relationship as indicated in FIG. 2.

FIG. 3 is a perspective view, partly in section, of the carton, in a sealed condition.

Also shown are dust flaps l6 and 18 which in this case are folded in between the inner and outer flaps.

The outer flap 12 is oversized and has a main panel 20 plus an extension panel 22 which is folded in along a fold line 24 corresponding to a corner line of the carton so that it lies in between the main panel 20 and the underlying inner flap 14.

In accordance with the invention only one surface of the sheet material forming the carton is coated with a thermoplastic adhesive which is placed on top of the clay fill which is usually present to limit the amount of thermoplastic adhesive required to act as an ink-receptive surface for printing on the carton as well as to form adhesive coats for sealing the end closures.

Because of the folding in of the extension panel 22, it will be noted that the seal 26 is between the face-to-face adhesive surfaces on the bottom of the extension panel 22 and on the top of the inner flap l4 and, there being no adhesive on the faceto-face surfaces on top of the folded in extension panel 22 and on the bottom side of the main panel 20, there is no adhesive seal within the fold-in. Accordingly if the main panel is formed with two parallel lines of perforations 30 and 32, that portion of the main panel therebetween can act as a tear strip 40 which can be removed from the carton to open the same without having to break the adhesive seal 26. In this case the perforation line 32 is at or near the fold line 24.

As shown in FIGS. 4 and the corners of flaps l6 and 18 are cut off as are the side corners of extension 22, so that when closed these parts will not overlap but will lie in the same plane. This makes sealing of the extension to the inner flap more reliable because the dust flaps do not tend to keep the two panels away from each other.

FIGS. 6 and 7 show a similar box but here the dust flaps 16a and 18a are folded in first and then front flap 14a is folded over the dust flaps so that it lies between the dust flaps and the extension 22. The corners therefore are not cut off.

The embodiment shown in FIGS. 8-10 is substantially identical with the exception of the placement of the lines of perforation. In this case both lines of perforations 42 and 44 are formed along the corner lines of the carton and along the lines of connection between the two sealing flaps l2 and 14 and the body of the carton. Thus the tear strip is constituted of the main panel 20, the extension panel 22, and, sealed to it, the inner flap 14.

A thumb breakaway portion 45 may also if desired be formed in the side of the carton in order that the one who opens the carton may secure a better grip on the top tear-off strip. In this case too however there is no rupture of the closure seal 26 during the removal of the tear strip.

It thus can be seen that there is provided an end closure for a carton which does not require coating a sheet material, from which the single piece carton is made, with adhesive on both sides. A tear strip which can be removed without rupturing the adhesive seal may extend along the edge of the carton leaving a substantial portion of the main end panel intact for reuse to reclose the carton, and the seal can still be along the edge. This is highly desirable as it is easier to seal near the sidewall of a carton than it is at unsupported portions of the end panels between the sidewalls.

What is claimed is:

l. A carton formed from a single sheet of material and having a sealed end closure which includes,

inner and outer end flaps folded inwardly counterdirectionally into overlapping relationship,

said outer flap being oversize and having a full-size main panel and an extension panel,

said extension panel being folded inwardly between said main panel and the underlying inner flap along a fold line extending substantially along a comer line of the carton, and,

an adhesive coating on the outer surface of said sheet material formed into a face-to-face adhesive seal between said inner flap and said extension panel.

2. A carton as claimed in claim 1, wherein the other surface of said sheet material is a nonadhesive surface so that the upper face of the folded-in extension panel and the under face of the portion of the main panel which it underlies are con nected but unsealed to each other.

3. A carton as claimed in claim 2, wherein the outer flap has two parallel lines of perforations forming therebetween a removable tear strip for opening the carton.

4. A carton as claimed in claim 3, wherein one of said lines of perforation extends along the line of connection between said main panel and said folded-in extension panel.

5. A carton as claimed in claim 3, wherein said tear strip overlies said folded-in extension panel and is removable from the carton without breaking the seal between said extension flap and said underlying inner flap.

6. A carton as claimed in claim 2, wherein the carton has parallel lines of perforations extending along the corner lines of the carton where said flaps are folded inwardly whereby both said flaps may be torn away from said carton without breaking said adhesive seal to open said carton.

7. A carton as claimed in claim 1 having a pair of dust flaps folded inwardly counterdirectionally, said extension panel and said dust flaps being contoured to lie, without overlapping each other, in a single plane between the planes of said main panel and said inner flap. 

1. A carton formed from a single sheet of material and having a sealed end closure which includes, inner and outer end flaps folded inwardly counterdirectionally into overlapping relationship, said outer flap being oversize and having a full-size main panel and an extension panel, said extension panel being folded inwardly between said main panel and the underlying inner flap along a fold line extending substantially along a corner line of the carton, and, an adhesive coating on the outer surface of said sheet material formed into a face-to-face adhesive seal between said inner flap and said extension panel.
 2. A carton as claimed in claim 1, wherein the other surface of said sheet material is a nonadhesive surface so that the upper face of the folded-in extension panel and the under face of the portion of the main panel which it underlies are connected but unsealed to each other.
 3. A carton as claimed in claim 2, wherein the outer flap has two parallel lines of perforations forming therebetween a removable tear strip for opening the carton.
 4. A carton as claimed in claim 3, wherein one of said lines of perforation extends along the line of connection between said main panel and said folded-in extension panel.
 5. A carton as claimed in claim 3, wherein said tear strip overlies said folded-in extension panel and is removable from the carton without breaking the seal between said extension flap and said underlying inner flap.
 6. A carton as claimed in claim 2, wherein the carton has parallel lines of perforations extending along the corner lines of the carton where said flaps arE folded inwardly whereby both said flaps may be torn away from said carton without breaking said adhesive seal to open said carton.
 7. A carton as claimed in claim 1 having a pair of dust flaps folded inwardly counterdirectionally, said extension panel and said dust flaps being contoured to lie, without overlapping each other, in a single plane between the planes of said main panel and said inner flap. 